Li containing garnet materials have been attracting considerable interest as potential solid state electrolytes for Li ion batteries. In such Ln3M2LixO12 (Ln= lanthanide, alkaline earth; M=Zr, Hf, Sn, Nb, Ta, Sb, Bi, Te) the best Li ion conductivity is observed for Li contents, x, just below the maximum 7.0. The decrease in conductivity for x=7.0 systems is related to Li ordering (cell changes from cubic to tetragonal) to prevent too short Li-Li interactions. In this work, we report a combined experimental and modelling study of Ce4+ doping in La3Zr2Li7O12. We show for the first time that Ce4+ can be doped onto the Zr4+ site in this material. This doping strategy results in a reduction in the tetragonal distortion as well as a lowering of the temperature of the tetragonal-cubic phase transition, attributed to the increase in cell size reducing Li-Li interaction strain. Coupled with these changes, the conductivity shows a significant (two orders of magnitude) improvement. Furthermore, the Ce doping also reduces the interfacial resistance (388 Ωcm2 for Li7La3Z1.75Ce0.25O12) in contact with Li metal, giving additional potential benefits to this doping strategy. The long-term cycling stability of a Li//garnet//Li symmetric cell over 190 h has been demonstrated.

An electrochemical cell for in-situ neutron powder diffraction studies of electrode materials for lithium-ion batteries is presented. The device has a coin cell geometry, consisting of 8.4 cm diameter, circular components that can be stacked together and clamped tight using sixteen polyetheretherketone (PEEK) screws. The background issue associated with incoherent scattering from hydrogen within the organic electrolyte was addressed by replacing the normal electrolyte with a deuterated analogue, significantly improving the peak-to-background ratio of the in-situ neutron data. Initial in-situ studies showed clear structural evolution within Li_xCoO₂ during charge in a half-cell with lithium metal as the counter electrode, in agreement with previous studies. In addition, the in-situ cell was shown to provide electrochemical performance comparable to that of equivalent coin cells of the commercial design and, following these demonstration studies, is available for in-situ structural studies of other lithium cathode and anode materials during charge/discharge cycling.

Tetragonal Li₇La₃Zr₂O₁₂ (LLZO) was halogenated to form cubic LLZOF(Cl) via a low temperature solid state synthetic route using PTFE and PVC polymers.